1. Field of the Invention
The present invention relates to an inkjet printer.
2. Discussion of the Background
In such inkjet printers, a plurality of inkjet heads corresponding to each color is arranged in a head device. Printing of desired characters or graphics, designs, photographs, etc. is performed by discharging ink drops from many nozzles provided in the inkjet heads and depositing ink layers on a printing medium. At this time, if a compatibility between the inkjet heads and the printer, or optimization of a driving method of the head device is inadequate, etc., ink drops called satellites (hereinafter, referred to as satellite ink drops) that are of a droplet-size smaller than the ink drops may be formed following the desired ink drops discharged by an ink discharge control.
Because a mass of these satellite ink drops is less than that of the desired ink drops, a dropping velocity of the satellite ink drops is easily affected by an air resistance. Furthermore, a dropping trajectory of the satellite ink drops is also easily affected by air currents caused by movement of the head device. As a result, the dropping velocity may rapidly decrease due to an influence of the air resistance of some of the satellite ink drops, moreover, the dropping trajectory may deviate from a desired trajectory due to an influence of the air current caused by the movement of the head, and ink drops called mist (hereinafter, referred to as ink mist) that float inside the printer (between the head device and the printing medium) without depositing on a surface of the printing medium may be produced. The ink mist thus generated deposits on nozzle surfaces of the inkjet heads and causes discharge failure. Furthermore, it deposits on other structural members of the printer and stains them. Damage from such mist becomes further prominent in cases where printing is performed is a situation where there is a comparatively bigger gap between the nozzle surface (a surface on which many nozzles are formed) of the inkjet heads and the printing medium. Such a situation arises, for example, when printing is performed on a surface of a textured printing medium, or in textile inkjet printers where fluffiness of a fabric needs to be avoided.
Conventionally, an inkjet printer (for example, see Japanese Patent Application Laid-open No. S62-111749) that includes a mist suction path and an ink mist suction unit is known as a countermeasure against such ink mist. In this inkjet printer, there is provided a suction fan that is arranged separately from the head devices, and the mist suction path is connected integrally with the head devices via the suction fan and an air suction tube. The ink mist suction unit sucks the ink mist, which is generated during printing, along with air from a suction port of the mist suction path using the suction fan and captures the ink mist using built-in filters arranged in the mist suction path. Moreover, in a drying unit disclosed in Japanese Patent Application Laid-open No. S62-111749, the air passing through the filters is not exhausted to the outside from an exhaust port of the suction fan; however, it is guided to a discharge path arranged in the head device via an air supply tube installed in the exhaust port. After the air is heated using a built-in heater arranged in the discharge path, it is discharged from a discharge port of the discharge path onto an already printed portion on the printing medium and the ink is dried.
However, in the conventional ink mist countermeasure described above, the suction port that sucks the ink mist opens opposite the printing medium, and the air between the head device and the printing medium is sucked almost in a perpendicular direction with respect to the printing medium. Moreover, the head device sucks the air while moving with respect to the printing medium. Therefore, the air between the head device and the printing medium cannot be sucked smoothly and the ink mist cannot be removed effectively. To solve this problem, it may be considered to increase a suction force of the suction port by increasing a number of rotations of the suction fan. However, this method required special suction fans having a high suction force, or to provide plural suction fans. Therefore, particularly, while applying to large-size inkjet printers, this method presented problems of increased cost and loud noise.